Investigation of bubble instabilities in film blowing process / J. Laffargue in INTERNATIONAL POLYMER PROCESSING, Vol. XVII, N° 4 (12/2002)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XVII, N° 4 (12/2002) . - p. 347-353 Titre : Investigation of bubble instabilities in film blowing process Type de document : texte imprimé Auteurs : J. Laffargue, Auteur ; L. Parent, Auteur ; P. G. Lafleur, Auteur ; P. J. Carreau, Auteur ; Y. Demay, Auteur ; Jean-François Agassant, Auteur Année de publication : 2002 Article en page(s) : p. 347-353 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : This paper describes an original on-line video device developed in order to study bubble instabilities occurring in the film blowing process, taking into account their three-dimensional behavior. For a linear low-density polyethylene, two forms of instabilities and combination have been observed : draw resonance and helical instability. These instabilities could be quantitatively described and differences in behavior could be assessed using real objective measurements and criteria. The influence of key processing conditions was investigated and the results showed that the instabilities are enhanced by increasing the draw ratio, blow up ratio and frost line height. These first results are in agreement with the majority of the results reported in the literature, but allow for a more accurate analysis of the phenomena. Note de contenu : - EXPERIMENTAL : The film blowing unit - On-line measurements - TYPICAL EXAMPLES : Stable bubble - Draw resonance instability - Helical instabilities - PRIMARY RESULTS : Objectives - Low FLH - High FLH - Construction of bubble stability map DOI : 10.3139/217.1704 En ligne : https://drive.google.com/file/d/1eUnHlunNemzsRduWllrIyGWzJa2MxID9/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=16038 [article]

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Investigation of Polymer Stretching Instabilities : Application to Film Blowing / J. Laffargue in INTERNATIONAL POLYMER PROCESSING, Vol. XXV, N° 5 (11/2010)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXV, N° 5 (11/2010) . - p 356-371 Titre : Investigation of Polymer Stretching Instabilities : Application to Film Blowing Type de document : texte imprimé Auteurs : J. Laffargue, Auteur ; Y. Demay, Auteur ; Jean-François Agassant, Auteur Année de publication : 2010 Article en page(s) : p 356-371 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Matières plastiques -- Soufflage -- Défauts Tags : 'Matière  plastique'  'Défaut  de  soufflage'  'Instabilité  hélicoïdale'  Etirement  Elongation  'Théorie  la  coquille'  Homogénéisation Index. décimale : 668.9 Polymères Résumé : Film blowing, as other elongational polymer forming processes, may present marked drawing instabilities leading to unacceptable products. But in film blowing, these instabilities are much more complex than for example in fibre spinning: there is no stabilizing effect of the polymer cooling, and the symmetry of the process may be broken, leading in some processing conditions to so called helical instabilities. Stability of the process has been investigated using a strategy inspired from shell or homogeneisation theory: as the classical approach uses a frame locally affixed to the membrane, the equations of the problem are now written in the cartesian laboratory frame. Making the equations dimensionless introduces naturally a small parameter defined as an aspect ratio (ratio of the film thickness to the bubble radius). Kinematic and stress variables are expanded as a function of this small parameter and introduced in the equations. It leads classically to a sequence of equations at successive orders. This strategy is used to obtain a time dependent membrane model. The stationary solution is equivalent to the one obtained using the classical approach. This model allows to develop a stability analysis, first in the axisymmetric case and then in the non axisymmetric one. Even a crude Newtonian temperature dependent rheology allows to capture qualitatively the observed instability phenomena. DOI : 10.3139/217.2347 En ligne : https://drive.google.com/file/d/19Dl90VAwpAYDwpH-gwjcrZckf1K2Hl_P/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=10254 [article]

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